1. Field of the Invention
The present invention relates to control systems/control methods for at least partially automated vehicular mechanical transmission systems, and, in particular, to control systems/control methods for at least partially automated mechanical transmission systems of the type which implement or allow a shift from neutral into a selected gear ratio when the speed of a controlled transmission shaft, such as the input shaft, is caused to be within a given range of the synchronous speed for that shaft in the selected ratio and at the sensed speed of another transmission shaft, such as the output shaft or a mainshaft.
More particularly, the present invention relates to a control system/method for an at least partially automated vehicular mechanical transmission wherein, at start from stop conditions, the range or "window" of controlled shaft rotational speeds at which jaw clutch engagement is initiated/permitted is considerably greater than the range or window utilized for running shifts, and/or the input shaft is monitored for indications of improper inertia brake/input shaft brake operation and/or input shaft drag caused by improper master clutch disengagement and, if such conditions are sensed, the range or window of input shaft speeds at which jaw clutch engagement is initiated/permitted is modified to a value which is very much greater than the range or window of input shaft speeds utilized for running (i.e. on the move) gear changes.
2. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Such fully automatic change gear transmission systems include automated transmissions wherein pressurized fluid is utilized to frictionally engage one or more members to other members or to a ground to achieve a selected gear ratio as well as automated mechanical transmissions utilizing electronic and/or pneumatic logic and actuators to engage and disengage mechanical (i.e. positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065 and 4,361,060, the disclosures of which are hereby incorporated by reference.
Such fully automatic change gear transmissions can be unacceptably expensive, particularly for the largest heavy-duty vehicles which are not typically sold in high volumes. Additionally, those automatic change gear transmissions utilizing pressurized fluid and/or torque converters tend to be relatively inefficient in terms of power dissipated between the input and output shafts thereof.
Semi-automatic transmission systems utilizing electronic control units which sense throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement operator manually selected transmission ratio changes are known in the prior. Examples of such semi-automatic transmission systems may be seen by reference to U.S. Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
While such semi-automatic mechanical transmission systems are very well received as they are somewhat less expensive than fully automatic transmission systems, allow manual clutch control for low speed operation and/or do not require automatic selection of the operating gear ratio, they may be too expensive for certain applications as a relatively large number of sensors and automatically controllable actuators, such as a master clutch and/or a fuel throttle device actuators, are required to be provided, installed and maintained.
Partially automated transmission systems including a semi-automatic shift implementation system/method for a mechanical transmission system for use in vehicles having a manually only controlled engine throttle means, and a manually only controlled master clutch are discussed in the above-mentioned copending related patent applications. These systems include a control/display panel or console for operator selection of upshifts, downshifts or shifts into neutral, an electronic control unit (ECU) for receiving input signals indicative of transmission input and output shaft speeds and of manually selected shifts and for processing same in accordance with predetermined logic rules to issue command output signals and a transmission actuator for shifting the transmission in accordance with the command output signals.
The control/display device will allow the operator to select/preselect a shift into a higher ratio, a lower ratio or into neutral and preferably will display the selected but not yet implemented shift as well as the current status of the transmission. Upon the driver manually causing synchronous conditions to occur, the selected shift will automatically be implemented.
Another type of partially automated vehicular mechanical transmission system may be seen by reference to U.S. Pat. No. 4,676,115, the disclosure of which is incorporated herein by reference, and involves sensing values indicative of input and output shaft speeds and not permitting a jaw clutch engagement to be attempted until substantially synchronous conditions are sensed.
In the prior art partially automated vehicular mechanical transmission systems at start from stop conditions the system, when sensing and/or anticipating synchronous, has a "band" or range of speeds that it considers synchronous, called a "window". The prior art systems were not totally satisfactory as, when the vehicle, such as a truck, is at or near zero speed, the "window" be a range of speeds at or near zero input shaft speed. When the driver commands a start gear, he selects the gear, then pushes in the clutch to the bottom of travel to disengage the clutch and actuate the input brake to stop the transmission input shaft. If the input brake is not working properly and/or the clutch pressure plate is warped, the input shaft will slow down at an abnormally slow rate resulting in engagement not being obtainable or in an unacceptable delay in engaging the start gear (a low forward reverse ratio).
Also, if the start gear is engaged at vehicle start from stop when the input shaft is stopped, the driver may not be provided with a positive feedback of jaw clutch engagement.